Solve for $x$ and $y$ using substitution. ${-2x-y = 7}$ ${x = -y-4}$
Since $x$ has already been solved for, substitute $-y-4$ for $x$ in the first equation. ${-2}{(-y-4)}{- y = 7}$ Simplify and solve for $y$ $2y+8 - y = 7$ $y+8 = 7$ $y+8{-8} = 7{-8}$ ${y = -1}$ Now that you know ${y = -1}$ , plug it back into $\thinspace {x = -y-4}\thinspace$ to find $x$ ${x = -}{(-1)}{ - 4}$ $x = 1 - 4$ ${x = -3}$ You can also plug ${y = -1}$ into $\thinspace {-2x-y = 7}\thinspace$ and get the same answer for $x$ : ${-2x - }{(-1)}{= 7}$ ${x = -3}$